I wrote a small plugin for Supybot, an IRC bot written in Python, to keep track of the main Gnash repository for our Freenode channel #gnash. The channel bot GnashGordon can show commit log messages, the current status of the repository, and generate diffs. It's now available under the GPL v3 at https://code.launchpad.net/supybot-bzr in - of course - a bzr repository.

There isn't a great demand for this sort of thing, but it seems to be the only such plugin out there, and of course it can be greatly improved if anyone has the time and motivation to do it.